Environmental Sensors and Subsystems

Print or save page as PDF
Adaptation of a Microscale GC for VOC Determinations of Biomarkers of Exposure/Disease in Breath and Saliva
Jonathan Bryant-Genevier, Sun Kyu Kim, Nicholas Eddy, and Edward T. Zellers

This project seeks to adapt a recently developed microfabricated gas chromatograph (µGC) field prototype, SPIRON, to the analysis of volatile organic compounds (VOCs) in human breath and saliva. The first application being pursued is the analysis of diacetyl, a butter substitute and insidious lung toxicant used in the food manufacturing industry, in saliva. Key components of this research include development of a sparger to purge diacetyl from (artificial) saliva samples into the SPIRON sampling module, quantitative capture, transfer and injection of diacetyl into the separation columns, separation of diacetyl from endogenous VOCs in saliva, and detection via an array of thiolated gold nanoparticle chemiresistor sensors, with ligands n-octaniethiol (C8), 6-phenoxyhexane-1-thiol (OPH), 4-(phenylethynyl)-benzenethiol (DPA), and methyl-6-mercaptohexanoate (HME). Results, thus far, have demonstrated successful sparging of diacetyl from artificial saliva at 60 ºC within 2L at 100 mL/min, effective capture/preconcentration of diacetyl by onboard sampler/µfocuser, and separation of diacetyl from several expected interferences. The CR array can provide an LOD of 6.4 ng based on the least sensitive sensor in the array, and the response pattern for diacetyl has been determined. Modifications to the signal circuitry and data processing have significantly improved the sensor signal stability and signal to noise ratio. The image above displays a conceptual sketch of (a)the sparging apparatus, (b) the fully assembled SPIRON field prototype with sparger attachment, and (c) a chromatogram of diacetyl with interferences generated with the SPIRON prototype (peaks 1, 3-9: acetone, THF, TCE, heptane, toluene, PCE, ethyl benzene, and xylene). The second application concerns the detection of a set of presumptive breath biomarkers of tuberculosis (TB), and entails adapting the fluidic components, materials, and operating conditions of the sampling module and (micro)analytical subsystem to detect selected the VOC biomarkers in high-humidity samples. Work on this application is ongoing. These projects have been funded by a Pilot Project Grant from NIOSH administered through the Michigan Center for Occupational Health and Safety Engineering.

Updated 04/05/2012